The present invention relates to an oxidizing composition for treatment of keratin fibers comprising a combination of； (a) at least one anionic associative copolymer, (b) at least one anionic non associative copolymer； (c) at least one peroxide agent； (d) at least one persulfate agent； (e) at least on alkalizing agent； and (f) a carrier medium suitable for hair treatment. The oxidizing composition described is suitable for composition used in conventional hair treatments such as dyeing, bleaching, and permanent waving or relaxing/straightening of the keratinous fibers, particularly human hair, requiring an oxidizing composition. The composition has good rheology, maintaining its consistency in use, and reduced swelling behaviour in use. Preferred anionic associative copolymer is acrylates copolymer and preferred anionic non associative copolymer is acryltes/beheneth-25 methacrylate copolymer.
